Thermoelectric modules are used for generating electricity using the Seeback effect or for cooling objects using the Peltier effect.
Different temperatures of two sides can be converted into electrical voltage. This is called the Seeback effect. Examples of thermoelectric modules using the Seeback effect include waste-heat thermoelectric generators, body-heat thermoelectric generators for small electronic devices such as electronic clocks, radioactive-decay-heat thermoelectric generators for spacecrafts.
When an electric current flows through two sides, heat is transferred from one side to the other side. Thus, one side is cooled and the other side is heated. This is called the Peltier effect. Therefore, it is possible to provide thermoelectric cooling devices that can cool objects only using an electric current without using a mechanical cooling cycle.
In general, thermoelectric cooling devices have low efficiency as compared with traditional compressor cooling devices. However, the thermoelectric cooling devices do not produce mechanical noise and are advantageous in precise and fast temperature controlling. In addition, the thermoelectric cooling devices have a relatively high efficiency at an operation temperature of about 5 to about 10 degrees Celsius or in small-sized applications.
An exemplary thermoelectric module of the related art will now be described with reference to the accompanying drawing.
Referring to FIG. 1, a thermoelectric module 10 includes an upper substrate 11 and a lower substrate 12. The upper and lower substrates 11 and 12 absorb or emit heat. The upper and lower substrates 11 and 12 are vertically disposed at a predetermined distance apart from each other.
An N-type semiconductor 15 and a P-type semiconductor 16 are disposed between the upper and lower substrates 11 and 12. Each of the N-type semiconductor 15 and the P-type semiconductor 16 is formed of a thermoelectric material and has a predetermined size and shape. Practically, N-type semiconductors 15 and P-type semiconductors 16 are disposed in turn between the lower substrates 15 and 16.
A connection line 17 is disposed between the upper substrate 11 and the N-type and P-type semiconductors 15 and 16. The connection line 17 connects the N-type and P-type semiconductors 15 and 16.
A metal layer 25 is disposed under the connection line 17. The metal layer 25 prevents atoms from moving from the connection line 17 to the N-type and P-type semiconductors 15 and 16. The metal layer 25 is formed of nickel (Ni) having a small amount of phosphor or boron.
That is, the metal layer 25 prevents deterioration of thermoelectric characteristics of the thermoelectric module 10 and stabilizes the thermoelectric characteristics of the thermoelectric module 10. The metal layer 25 is formed on the connection line by a predetermined coating method.
A barrier layer 27 is disposed between the N-type and P-type semiconductors 15 and 16. The barrier layer 27 prevents the N-type and P-type semiconductors 15 and 16 from being contaminated by a soldering layer 26.
The soldering layer 26 is disposed between the metal layer 25 and the barrier layer 27. The soldering layer 26 bonds together the metal layer 25 and the barrier layer 27.
An N contact 20 and a P contact 21 are disposed on a bottom surface of a lower soldering layer 26.
The N and P contacts 20 and 21 are spaced apart from each other and are attached to bottom surfaces of the N-type and P-type semiconductors 15 and 16 for supplying power to the N-type and P-type semiconductors 15 and 16.
However, the thermoelectric module 10 of the related art has the following problems. The soldering layers 26 are disposed at top and bottom surfaces of the N-type and P-type semiconductors 15 and 16 for fixing the N-type and P-type semiconductors 15 and 16 to the upper and lower substrates 11 and 12.
That is, the thermoelectric module 10 contains a harmful material that may affect operator's health. Furthermore, due to the soldering layer 26, the barrier layer 27 is additionally necessary. This increases the thickness of the thermoelectric module 10 and the number of manufacturing operations of the thermoelectric module 10, resulting in a high defect rate.
Moreover, since a soldering operation for forming the soldering layer 26 consumes much time, the productivity of the manufacturing operations of the thermoelectric module 10 is low, and thus the price of the thermoelectric module 10 is high.